1. Field of the Invention
This invention relates to a thin film magnetic head, a magnetic head device, a magnetic recording/reproducing device and a method for fabricating a thin film magnetic head.
2. Related Art Statement
In a magnetic recording field, a thin film magnetic head having a spin-valve film (hereinafter, called as a “SV film”) as a reading element is mainly employed for developing the recording density and the miniaturization.
The SV film is composed of a pinned layer, a non-magnetic layer and a free layer which are stacked in turn. The magnetization of the pinned layer is fixed in a given direction, and the magnetization of the free layer is rotated commensurate with an external magnetic field. The resistance of the SV film is minimized as the direction of the magnetization of the pinned layer is parallel to that of the free layer, and the resistance of the SV film is maximized as the direction of the magnetization of the pinned layer is anti-parallel to that of the free layer. Therefore, a given external magnetic field is detected by measuring the change in resistance as the free layer is rotated.
In addition, a magnetic domain-controlling film is prepared to apply a perpendicular biasing magnetic field to the free layer. In this case, the free layer is made single domain to prevent Barkhausen noise due to the movement of magnetic wall. The magnetic domain-controlling film may be made of a given antiferromagnetic film. In this case, the perpendicular biasing magnetic field is applied through the bonding with exchange interaction between the antiferro-magnetic film and the magnetic film constituting the free layer. Moreover, the magnetic domain-controlling film may be made of a hard magnetic film. In this case, the perpendicular biasing magnetic field is applied from the hard magnetic film. The former biasing means is called as exchange biasing method, and the latter biasing means is called as hard magnetic biasing method.
In the area of the SV film adjacent to the magnetic domain-controlling film, only the perpendicular biasing magnetic field is generated larger, and a longitudinal biasing magnetic field is not almost generated to form a non-sensitive region, which does not function as a sensor and increase the electric resistance of the magnetic resistive sensor circuit. As the electric resistance of the magnetic resistive sensor circuit is increased, the performance of the magnetic resistive sensor circuit is restricted and electro-migration due to large current density may occur.
In order to decrease the electric resistance of the non-sensitive region, a so-called lead overlaying structure where electrode films are provided at both sides of the SV film beyond the non-sensitive region.
In order to realize the lead overlaying structure, such technique is disclosed in Japanese Patent Application Laid-open No. Tokukai Hei 11-53716 (JP A 11-53716) as that a first electrode film not constituting a lead overlaying structure is formed on a magnetic domain-controlling film, and a second electrode film constituting the lead overlaying structure is formed on the first electrode film by means of reactive ion etching (RIE).
With the above technique, however, since the second electrode film is formed by means of RIE, the rising angle of the second electrode film becomes large to be 60-80 degrees.
In a thin film magnetic head having such a lead overlaying structure, a gap film made of an inorganic film is formed on electrode films and a magnetoresistive effective film by means of sputtering, and a shielding film is formed on the gap film. When the rising angle of a second electrode film is set within 60-80 degrees as mentioned above, however, the gap film can not be formed sufficiently thick at the rising surface of the second electrode film, so that electric insulation can not be created between the second electrode film and the shielding film to be formed on the gap film.
In order to realize the lead overlaying structure, such a technique is also disclosed in Japanese Patent Application Laid-open No. 2000-276719 as to form an electrode film constituting a lead overlaying structure by means of lift-off.
With the lift-off technique, however, the lead overlaying structure is formed in wedge so that the electrode film is risen from on the magnetoresistive effective film by a constant angle, and thus, the forefront of the electrode film is formed in thin blade. Therefore, a large current density is generated at the blade-shaped forefront of the electrode film, and thus, electro-migration due to the larger current density may occur.